Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

H,W=map(int,input().split())
s=[list(input()) for _ in range(H)]


d=deque()
d.append([0,0,0])
s[0][0]="0"
mx=[1,0,-1,0]
my=[0,1,0,-1]
ans=0

white=0
for i in range(H):
    for j in range(W):
        if s[i][j]==".":
            white+=1

while len(d)>0:
    t,y,x=d.popleft()
    if [y,x]==[H-1,W-1]:
        break
    for m in range(4):
        if 0<=y+my[m]<H and 0<=x+mx[m]<W and s[y+my[m]][x+mx[m]]==".":
            d.append([t+1,y+my[m],x+mx[m]])
            s[y+my[m]][x+mx[m]]=str(t+1)

if s[-1][-1]==".":
    print(-1)
else:
    print(white-int(s[-1][-1]))